In recent years, development of displays has rapidly progressed, and various displays such as a liquid crystal display and an EL display have been extensively used for office automation equipment such as a personal computer and a word processor. These displays have a sandwich structure in which a display element is disposed between transparent conductive films.
A silicon-based semiconductor film is mainly used for a switching device (e.g., thin film transistor (TFT)) that drives a display. A silicon-based thin film exhibits excellent stability, excellent workability, a high TFT switching speed, and the like. A silicon-based thin film is generally formed by chemical vapor deposition (CVD).
An amorphous silicon-based thin film has a problem that a high-speed animation or the like cannot be displayed at a high frame rate due to a relatively low switching speed. A crystalline silicon-based thin film achieves a relatively high switching speed, but requires a high temperature of 800° C. or more, laser heating, or the like for crystallization. Specifically, a large amount of energy and a large number of steps are required for producing a crystalline silicon-based thin film. A silicon-based thin film exhibits excellent performance as a voltage device, but shows a change in characteristics with time when causing a current to flow therethrough.
In view of the above situation, an oxide semiconductor film has been studied as a film as an alternative to a silicon-based thin film. For example, Patent Document 1 discloses an oxide semiconductor pn-junction device, and discloses a transparent semiconductor thin film formed of zinc oxide and magnesium oxide as a semiconductor film that forms the device.
A transparent semiconductor thin film formed of zinc oxide and magnesium oxide is etched by a weak acid at a very high etching rate. However, since such a transparent semiconductor thin film is also etched by an etchant used for a metal thin film, the transparent semiconductor thin film may be etched together with a metal thin film formed on the transparent semiconductor thin film when etching the metal thin film. Therefore, the above transparent semiconductor thin film cannot be suitably used when selectively etching only a metal thin film formed on the transparent semiconductor film.
Patent Document 2 discloses an ITO sintered body that contains indium oxide (In2O3), tin oxide (SnO2), and scandium oxide (Sc2O3) as the main components so that the weight ratio satisfies the relationships “(In2O3+Sc2O3):SnO2=99 to 94:1 to 7” and “In2O3:Sc2O3=99.8 to 60:0.2 to 40”. The sintered body disclosed in Patent Document 2 contains 1 to 7 wt % of tin oxide, and functions as a conductive film instead of a semiconductor film since carriers are produced from tin oxide.
Patent Document 3 discloses a thin film that contains indium oxide, tin oxide, and yttrium oxide as the main components. Patent Document 3 relates to a transparent conductive film, and is silent about an oxide semiconductor.
An object of the invention is to provide a sintered body (sputtering target) that enables stable film formation of an indium oxide-based oxide semiconductor film.
Another object of the invention is to provide a sputtering target for producing an excellent crystalline oxide semiconductor film.    Patent Document 1: JP-A-2004-119525    Patent Document 2: JP-A-2000-143334    Patent Document 3: JP-A-2000-169219